1. Field of the Invention
The field of invention relates to means for measuring stress in the warp and woof of a woven fabric. As used hereinafter, "fabric" shall mean a woven fabric of warp and woof; "warp" is defined to mean the lengthwise threads of a woven fabric; and "woof" is defined to mean the crosswise threads of a woven fabric.
2. Description of the Prior Art
In recent years, heavy duty woven fabrics have been used as roofs for gymnasia, indoor tennis courts, indoor playgrounds, indoor ice skating rinks, pavilions, athletic stadia, enclosures for outdoor concerts, and the like. These building construction heavy-duty woven fabrics as a whole are secured to supporting building structures so as to sustain heavy snow and wind loads by maintaining the warp and woof of the fabric in appropriate stress conditions. Fabric roofs generally fall into two classes: (1) fabric roofs internally supported by air pressure; and (2) fabric roofs held in place primarily by tension stressing of the fabric. In both types of fabric structures, it is extremely important structurally to properly maintain the tension on the fabrics to prevent flapping and pounding, which will occur under certain wind conditions if the fabric becomes slack due to lessening or loss of tension.
However, until now, in the actual installation of fabric roofs, there has been no practical means for determining whether the fabrics are tensioned in accordance with design specifications. As a consequence, re-tensioning has depended on the experience and judgment of skilled workers who engage in fabric roof construction. Furthermore, even though the fabric may be properly pre-tensioned when installed, the tension in the fabric gradually relaxes with time. Therefore, in order to safely maintain and to control the fabric structures, it is necessary to properly evaluate the relaxation of actual fabric tension and to reintroduce tension as required. However, since there have been no effective means for measuring fabric stress, when to re-tension has been a judgment call by those responsible for building maintenance.